Concentration of minerals



Jan. 26, 1932. A. w. HAHN CONCENTRATION OF MINERALS Filed Feb. l, 1929 2 ed with the desired silver mineral.

Patented Jan. 26, 19,32

UNlTEn STATES PATENT OFFICE ALBERT W. HAHN, F SALT LAKE CITY, UTAH CONCENTRATION 0l* MINERALS Application mea :february 1, 192s. serial mi. 336,742.

cult middlings and remove them from the circuit.

The invention is particularly useful in the concentration of oxidized or partially oxidized ores. In certain ores, the silver-bearing minerals are in a form diiiicult to concentrate and recover by flotation and when high recoveries are obtained the grade of the concentrate is relatively low, as excess-ive amounts of barren gangue particles are ioat- These silver minerals, difficult to float, when returned to the notation circuit for re-treatment or when treated in separate fiotation machines drop out of the otation froth and produce a tailings or middling product relatively very high in silver values and high in barren gang'ue particles.

I propose, therefore, to segregate and remove these silver minerals, refractory to liotation concentration, instead of following the usual flotation practice of returning the tailings from the cleaner and the middlings concentrate to the circuit. By removing the relatively high silver-bearin flotation middling product and treating it separately by flotation, I have found by tests on vthe basis of treating approximately tons per day of mixed oxide and sulphide lead-silver silicious ores that the number of flotation cells necessary to obtain the same grade of final tailings is about 30 per cent less than when following the standard practice.

In .the concentration of ores by froth {iotation, particularly oxidized or partially oxidized ores, I propose therefore to take ofi` the highly siliceous concentrate or middling containing the refractory mineral or minerals, particularly the silver minerals, to subject this concentrate to further treatment as by Separate flotation or table concentration and todispose of the products, concentrates and tailings, from this separate treatment in such ways as will yield the maximum profit according to the character of the product.

For instance, if the concentrate from this separately treated product is high in lead it can be combined with a regular flotation lead concentrate. The tailings relatively high in silver and silicious gangue material can be advantageously smelted at a copper smelltler in which this type of material is desira e.

The accompanying drawing is a diagram illustrating by way of example an application of the invention to the concentration of mixed oxide-sulphide lead-silver ores.

Numbers l to 14 are successive cells of a main flotation unit. Supplementary flotation units are shown with three cells E, with four cells F and three cells H respectively. 'Inlie ore pulp enters the feed box of the principal fiotation unit at A and passes through the cells l to 14 in succession until the tailings are taken ofi' at B.

o The sulphide concentrates are first taken olf from cells 1 to 3, cleaned in the supplementary cells E and the finished sulphide concentrate taken off therefrom; the tail` ings passing o' at G being carried around by the line C to the head of the sulphide circuit, cell No. 1.

The oxide concentrates are taken off from cells 4 to 1l and cleaned in cells F from which the finished oxide concentrate is taken off. The tailings run ofl" at I and are carried around by the line D to the cell 4 which is the head of t-he oxide concentrate circuit.

The oxidized minerals are floated by adding to thecells sodium sulphide, amylxanthate and a frothing agent if necessary, in various quantities, and at each of the cells or in every other cell, depending on the nature of the ore; and at times, it may be necessary to add small amounts of sodium silicate.

From the last section of the main unit, cells 12, 13 and 14, there is drawn off a middlings; that is, a concentrate of lower value 4 than those taken oil from the previous cells.

In the ores to which this invention is particularly directed such middlings are high in gangue and in silver. They are difcult to float and they are particularly objectionable in this respect in the original pulp.

The removal of the middlings is effected in substantially the same manner as above set forth for the removal of the oxide concentrates.

I have found that the values in the ore can be more economically recovered by segregating these middlings and treating them separately. I limit the middlingsthus taken ofl` as far as is practicable to the distinct product which contains only negligible quantities of the more easily float-able minerals.

According to the diagram such middlings are separately concentrated in cells H, the middllng concentrate going to a lead smelter and the tailings at J to a copper smelter.

To illustrate the dropping out of the refractory silver mineral when an oxidized lead-silver flotation concentrate is subjected to a flotation cleaning Operation 'as in the cells F, I submit the following results obtained by laboratory tests and tonnage mill Oxide concentrate cleaner tests HEADS Au Ag Pb Cu Fe Insol. ozs. ozs.

CLEANER CONCENTRATES Au Ag Pb Cu Fe Insol. ozs. ozs.

CLEANER TAILS Au Ag Pb Cu l Fe Insol. ozs. ozs 7u 2s. 1a. 4 7. s 54. 2 25. 1 29. 2 7. 2 40. 2 26. 0 25. 1 6. 0 44. 9 18. 0 27. 3 6. 2 33. 2 29.2 34.4 6.1 37.8 24. 7 10. 3 8. 6 61. 4

The above table shows an increase in the lead content by the concentration, but no substantial increase in the silver content. And

Athe cleaner tails show in each case an increased percentage in silver; indicating that the silver minerals have dropped out of the froth or at least have not been floated therewith. I submit also the following table of similar tests on the oxide middlings which are passed through the cleaner I-I.

Om'de middling cleaner tests HEADS Au Ag Pb Cu Fe Insol ozs. ozs.

CLEANER CONCENTRATES Au Ag Pb Cu Fe Insol.

ozs. ozs.

TAILS Au Ag Pb Cu Fe Insol.

ozs. ozs

The middling being treated separately in this way, theconcentration brings about a substantial increase in the silver and lead. The metallic content of the tails however is high enough to make them worth adding to the charge in a copper smelter.

The following tables will illustrate the differences between the old method in which high recoveries are obtained, but with a low grade of concentrate, and the present method by which though the recoveries are lower, the concentration is relatively high. The raw material was a mixture of ores from the Tintic Standard Mining Company and the North Lily Mining Company. The results of the standard method of flotation are shown in the following Table A.

With the same ore, treated so as to obtain a better ratio of concentration, the results were in accordance with Table B.

of Table A The higher recoveries are shown in Table A Where, for example, the concentrates weigh 64.5 per cent compared'with 37 per cent in Table B; and where the recoveries for the separate metals are also greater in Table A than in Table B.

lin assaying the product, however, we have a substantially lower concentrates in Table A; 32.7 ounces oit silver in the concentration compared with 43.4.- ounces in Table B, and 5.05 ounces of silver in the tails ot Table A com-pared with 6.98 ounces in Table B.

With the same ore, treated by my present method over a period of eight days and approximately 600 tons, the results were in ac,- cordance with Table C.

Table C shows the improvement in concentration ratio compared with Table B without sacrificing recoveries of either silver or lead values.

This removal of refractory values from a flotation circuit can be applied to the treatment of ores other than those cited, and I do not wish to limit my invention to those ores. For instance, in the treatment of some copper ores containingy sulphide and oxide a middlngs concentrate and diverting it from the circuit for further treatmen 2. In the concentrating by froth flotation of mixed oxide-sulphide lead-silver ores, the method which consists in taking off sulphide concentrates, subjecting them to a cleaner and returning the tails to the head of the circuit, takin@ oil oxide concentrates, subjecting them to a c eaner and passing the tails to the head of the oxide circuit and taking ed a middlings concentrate, cleaning it and treating .the cleaner concentrates and tails outside of the froth oatation circuit to recover their values.

Tn witness whereof, T have hereunto signed copper mlnerals, some oxide copper mineral would act as the cited silver minerals, in which case the middlin containing the refractory copper minera would be removed from the circuit and Ytreated separately as indicated. l

Various other lmodifications may be made by those skilled in the art without `departure from the invention as defined in the following claims.

1. In the concentrating by froth flotation of mixed oxide-sulphide leadsilver ores the method which conslsts in taking oi sulphide concentrates, and returning the tails tothe head-of the circuit, taking oil' oxide concentrates, subjecting them to a cleaner and passing the tails to the head of the oxide circuit and taking ott subjecting them to a cleaner 

